New discoveries link vitamin D deficiency with many chronic diseases. Coaxed by the sun, it may stop cells from perilously misbehaving
RONALD KOTULAK
SPECIAL TO THE STAR
CHICAGO—As the sun begins to break through some mornings, its warming rays are resuming a critical role that has lain dormant most of the winter, coaxing our skin to make vitamin D.
Emerging research indicates that vitamin D is more important to our health than previously thought, leading an increasing number of scientists to challenge whether the fear of sun exposure has made us cover up too much.
Doctors are finding an increase in vitamin D deficiencies, even as researchers discover remarkable results from the vitamin that affects nearly every tissue in the body.
When women took vitamin D in multivitamin supplements over a long period, their risk of developing multiple sclerosis was reduced by 40 per cent, according to one study.
And a disturbing number of children who don't have enough vitamin D in their bodies are showing up with rickets, a crippling bone disorder thought to have been eradicated more than 70 years ago.
Vitamin D is a critical hormone that scientists are discovering helps regulate the health of more than 30 different tissues, from the brain to the prostate. It plays a role in regulating cell growth, the immune system and blood pressure, and in the production of insulin, brain chemicals and bone.
"We thought that vitamin D was a very narrow-acting substance," said Dr. Hector DeLuca of the University of Wisconsin, where vitamin D was first identified in the early 1900s, leading to the fortification of milk and some other foods that eliminated endemic rickets.
"The big surprise is that it's got a lot of important biological effects that probably contribute to our health and we're just now beginning to uncover them," said DeLuca. "Are we getting enough vitamin D? No we're not, especially in the winter."
Vitamin D is one of the body's many control systems. It acts like an emergency brake that helps stop cells from perilously misbehaving, as immune cells can do when they cause such autoimmune diseases as multiple sclerosis and as breast and prostate cells do when they turn cancerous. This protection declines as vitamin D levels drop.
University of Chicago microbiologist Yan Chun Li discovered just how that happens with high blood pressure. Vitamin D helps normalize blood pressure by keeping a pressure-increasing switch called renin in check.
New research indicates vitamin D malnutrition may also be linked to many chronic diseases such as cancer, chronic pain, weakness, chronic fatigue, multiple sclerosis and Type 1 diabetes, high blood pressure, mental illnesses — depression, seasonal affective disorder and possibly schizophrenia — heart disease, rheumatoid arthritis, psoriasis, tuberculosis and inflammatory bowel disease.
"A lot of people with aches and pains and marginal weakness could be helped by vitamin D supplements," said Dr. Paresh Dandona of the State University of New York at Buffalo who reported the first five cases of vitamin D deficient myopathy three years ago.
Researchers are finding that the current recommended daily allowances of vitamin D are probably far lower than the minimum amount necessary for optimum health.
Scientists are quick to warn that although people may need more vitamin D, mostly in the form of supplements in higher latitudes where sunlight is weak during winter, they should consult a physician before consuming large doses. Taking too much vitamin D can elevate levels of calcium in the blood, a potentially serious condition that can lead to nausea, vomiting, or even death. It is especially easy for children to overdose on vitamin D supplements.
Dark-skinned people have the highest risk for vitamin D deficiency because dark skin needs five to 10 times more sunlight than white to produce the same amount of the vitamin.
Even in summer the skin's vitamin D-making ability gets dampened from the increasing use of sunscreen, leading a growing number of health experts to challenge the advice given over the last two decades to avoid the sun at all costs in order to reduce skin cancer risk.
"The amount of vitamin D in our diet is totally inadequate," said Dr. Michael Holick of Boston University Medical Center, a leading vitamin D expert. "We are in an era of sunphobia — that is not being exposed to any direct sunlight — that's being promoted widely by the dermatology community and it's probably hurting people's health more than it's helping them.
"That message needs to be modified and moderated to a more sensible approach so that people can get a little bit of safe sun," he said.
Source: The Chicago Tribune